This invention relates to improved devices for actuating a valve or other controlled unit automatically in response to forces developed by an earthquake or other shock forces of predetermined magnitude.
A device embodying the invention may be of the general type disclosed in U.S. Pat. No. 4,185,507 issued Jan. 29, 1980 to Domyan, including a weight which is displaceable by shock forces relative to a support structure and which acts when displaced to operate a mechanism serving to close a valve or actuate another controlled unit. Other similar shock responsive devices are shown in U.S. Pat. Nos. 4,475,565, 4,503,717, 4,513,629 and 4,603,591. In each of these, the shock actuated mechanism may include a tubular element disposed about a pedestal on which the weight is located, with the tubular element being actuable downwardly by the weight when the weight is displaced laterally from its normal position on the pedestal. In some of these prior arrangements, the shock responsive mechanism acts directly and mechanically to close off a gas valve or the like when subjected to shock forces. In U.S. Pat. No. 4,513,629, the mechanism functions to open a pilot valve, which admits compressed air or other pressure fluid to an actuator, which is then operated by the force of the pressure fluid to close a main valve or actuate another controlled unit.